Moser was dominant from the mid-1970s to the early 1980s and won the 1984 Giro d'Italia, the 1977 world road racing championship and six times in three of the five classics. He turned professional in 1973, showing a stylish pedaling style. But his powerful build meant he wasn’t a gifted climber. His 273 road victories puts him behind Eddy Merckx (525) and Rik Van Looy (379), but ahead of Rik Van Steenbergen (270) and Roger De Vlaeminck (255). He was also an accomplished track rider, riding up to six Six-Day races almost each winter throughout his career. He rode 35, 14 of which with René Pijnen, winning 15. A nephew Moreno Moser (born 25 December 1990) is an Italian professional racer.

On 19 January 1984, in Mexico City, Moser broke the 1972 hour record of Eddy Merckx. He rode 50.808 kilometers, on an aerodynamic bike with full disc wheels more advanced than the conventional bike Merckx used in 1972. As a result, in 1997 the Union Cycliste Internationale banned hour records set on bikes featuring technological advantages.[3] Under the new rules, Merckx's record wasn't broken until 2000. Moser auctioned his bicycle to benefit UNICEF.

In 1999, he admitted using blood doping in breaking the record, helped by sports doctor Francesco Conconi; his actions were not illegal at the time.[3] The 1984 record stood for more than nine years and Moser's ride brought aerodynamic technology to cycling. Moser retired in 1987.